Variable Capacitor Floating Diffusion Image Sensor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors face challenges in preventing image lag while improving sensitivity and HDR characteristics, as fixed capacitances of photoelectric conversion elements and floating diffusions lead to a trade-off between these features, particularly in miniaturized shared pixel structures.
Innovation Solution
The image sensor design incorporates a variable capacitor coupled to the floating diffusion, with a conductive pattern and variable electrode separated by a gap, allowing the effective capacitance to be adjusted via control signals, thereby optimizing capacitance values for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed capacitance values are used in photoelectric conversion elements and floating diffusions, then device structure is simple, but image lag cannot be prevented while improving sensitivity and HDR characteristics
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed capacitance structure into a variable capacitance structure. A variable electrode is introduced that can be positioned at different distances from the conductive pattern connected to the floating diffusion, allowing the capacitance value to be dynamically adjusted. When the variable electrode is closer to the conductive pattern, the capacitance increases to prevent image lag; when farther away, the capacitance decreases to improve sensitivity and HDR characteristics, thus resolving the contradiction between preventing image lag and improving image quality.
2Reliability
If capacitance values are optimized for improved sensitivity and HDR characteristics, then image quality is enhanced, but image lag occurs
Solution Approach 1:
The patent enables dynamic adjustment of capacitance values through the variable electrode mechanism. By controlling the position of the variable electrode relative to the conductive pattern, the system can switch between different capacitance states: a higher capacitance state to prevent image lag and a lower capacitance state to enhance sensitivity and HDR characteristics, thereby resolving the contradiction between image quality enhancement and image lag prevention.
Solution Approach 2:
The patent changes the capacitance parameter dynamically by adjusting the physical distance between the variable electrode and the conductive pattern. This parameter change allows the system to adapt to different operating conditions, switching between preventing image lag (higher capacitance) and improving sensitivity/HDR (lower capacitance), thus resolving the contradiction.
3Reliability
If variable capacitance structure is added to prevent image lag and improve performance, then image quality is enhanced, but device complexity increases
Solution Approach 1:
The variable electrode structure serves multiple functions: it acts as a capacitor element for adjusting capacitance values, and its positioning mechanism provides control over the capacitance state. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving the desired performance improvements.
Solution Approach 2:
The variable capacitor structure utilizes existing conductive patterns and interlayer dielectric layers from the standard sensor architecture, copying and adapting proven design elements rather than introducing entirely new complex structures. This approach minimizes the increase in device complexity while achieving variable capacitance functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the prevention of image lag while enhancing sensitivity and HDR characteristics, balancing the trade-off between these features without increasing pixel size, by dynamically changing the effective capacitance of the floating diffusion.
Implementation Method 1
a photoelectric conversion element configured to receive incident light and generate photocharges in response to the received incident light
Implementation Method 2
the conductive pattern and the variable electrode form a variable capacitor coupled to the floating diffusion and having a second capacitance value and operable to change an effective capacitance of the floating diffusion
Implementation Method 3
a variable electrode located apart from the conductive pattern by a gap, wherein the conductive pattern and the variable electrode form a variable capacitor
Data Source
AI summary
An image sensor device includes a photoelectric conversion element configured to receive incident light and generate photocharges in response to the received incident light; a floating diffusion coupled to the photoelectric conversion element to store the photocharges generated by the photoelectric conversion element, the floating diffusion having a first capacitance value; a conductive pattern electrically coupled to the floating diffusion; and a variable electrode located apart from the conductive pattern by a gap, wherein the conductive pattern and the variable electrode form a variable capacitor coupled to the floating diffusion and having a second capacitance value and operable to change an effective capacitance of the floating diffusion in response to a control signal applied to the variable electrode.